Modern fabric trim covers and their interconnected spring and cushion components (collectively termed “upholstery”), such as those used in vehicles, often carefully sculpted and shaped to produce a comfortable and aesthetically pleasing effect. As such, the fabric (typically cloth, vinyl or leather with an appropriate backing material) is secured at many locations along its surface to a resilient or flexible backing that defines the cushioned substrate of the upholstered item (for example, a seat bottom, cushion, back or headrest). The substrate is typically constructed from a resilient material. This resilient/flexible material can be synthetic foam (for example polyurethane and/or isocyanate-based foam) or another cushioning material, such as traditional rubberized horsehair, hog hair, and the like. In general, the close-fitting appearance of the upholstery to the substrate requires that the fabric be tacked down to the substrate at any intermediate dips, Vees or trenches in the surface. Otherwise, the fabric will tend to billow or “tent” at these non-planar surface features.
Traditional methods for tacking down trim covers at trenches entail the use of a plastic bead along the inner side of the trim cover. This bead is often located at an inner seam that is a sewn or welded, or otherwise adhered, joint between fabric pieces. Likewise the foam substrate includes an exposed metal wire that may be molded into the substrate along a trench in its surface during its construction. So-called “hog-rings,” consisting of bendable metal ringlets, are then secured to both the plastic bead and the metal wire. These rings are each applied by a tool, such as a hog-ring gun from a supply of wire. As each hog ring is secured, it forms an immovable, permanent joint between the fabric and the substrate. Clearly, this permanent joint is difficult to repair if needed and requires significant skill to create in the first place. In addition, this method of seat cover attachment leads to the development of injuries, such as carpal tunnel syndrome in employees who operate the hog ring tool over an extended period of time. Finally, the use of metal components may be undesirable where the seat includes electrical heating elements due to the metal's predisposition to conduct both heat and electricity.
More recently, trim covers have been secured to resilient substrates using detachable connections that allow repairs to be effected and are often more-easily applied without the used of highly skilled labor. In one example, one side of a hook and loop fastener is attached to a trench in the resilient substrate. The inner surface of the trim cover carries the opposing side of the fastener. This approach is reliable, but expensive, in terms of material wasted and consumed to attain a secure fit. It also requires a rather large-width trench to be formed in the resilient substrate to ensure a sufficient area of engagement between fastener sides.
Another recent approach involves the used of a series of clips that are molded into the trench as a foam substrate is manufactured. A version of this structure, and other prior art attachment mechanisms, are described in U.S. Published Patent Application US/2003/0215601 A1, entitled ATTACHMENT DEVICE, dated Nov. 20, 2003, by Peede, et al. the teachings of which are expressly incorporated herein by reference. A simplified version of such a clip and its use are shown in FIGS. 1-3 herein. As shown particularly in FIGS. 1 and 2, each clip 100 includes a pair of outwardly facing (with respect to the trim-cover-facing surface of the substrate) legs 102 that together form a female projection 104 with a pair of upper hooks or barbs 106 that face toward each other, thereby defining a top-end funnel, leading into a cavity 10. The barbs 106 define a narrow gap 112 therebetween. This gap 112 is smaller in width than the width of the cavity 110. The material and relative thickness of the legs 102 is such that the barbs 106 can be spread elastically apart so that an appropriately sized cylinder can pass between the legs to be thereafter trapped in the cavity against outward movement by the sprung-back barbs 106. In this case, the cylinder is the covered plastic or metal bead 120 (also known generally as “listing”) attached to a seam 122 between two trim cover fabric pieces 124 and 126. This bead assembly is also known as “listing” in the industry. In this example, the bead 120 is surrounded by a piece of non-woven covering 130 that retains the bead against the bottom of the seam 122 using stitching 132 (or another attachment mechanism). Collectively the diameter of the bead 120 and covering 130 define an outer diameter ODB approximately equal to, or slightly less than, the lateral width WB of the cavity 110. Thus, in operation, an installer need only press the bead 120 down between the barbs 106 (arrow 140) so that the angled funnel tops of the barbs cause the legs 102 to spread, allowing the bead 120 to pass therebetween. Once the bead 120 passes fully between the barbs 106, then the bead 120 is mechanically retained beneath the barbs 106 within the cavity, and the seam 122 (and facing cover 130), extend through the gap 112 to hold that particular part of the trim cover (124 and 126) against the clip 100.
The clip includes a base 150 having a relatively thin cross section and an increased surface area adapted to act as an anchor within the (foam) substrate material 252. As shown (FIG. 2), the base is disposed beneath the surface of a trench 254. The base is locked into the matrix of the substrate as a result of the molding process in which foam covers the base and adheres to the base's material. Typically, the clip 100 is mounted in the bottom of a trench 254 as shown. In this manner, sufficient setback is provided to allow the seam 122 to sink into the substrate for a taut fit against its surface.
FIG. 3 shows an exemplary vehicle seat foam cushion 310 according the prior art. A plurality of clips 100 are located along the trench at an appropriate degree of spacing so as to ensure that the bead of the trim cover defines a continuous, unsegmented shape. In the example of a seat bottom or back, approximately 12-30 clips may be needed to define a desired shape. In general, the tighter the curvature of the substrate, the smaller the clip spacing provided. The above-referenced published U.S. patent application contemplates that the spacing between clips can be regulated, in part, by providing fixed-space, flexible connectors between individual clips and molding such clips into the foam substrate with the predetermined spacing defined by the connectors.
The above-described prior art clips are typically constructed from a resilient material, which allows for the flexure imparted by insertion of the listing bead into their respective cavities. However, these clips should also adhere firmly to the foam or other resilient substrate material. Hence, the clip material should exhibit properties so that it appropriately adheres to the substrate so that it will not eventually detach under long-term use. Many polymeric materials, however, are not capable of enduring the requisite range of operating temperatures to which a vehicle interior and the underlying clips may be exposed—for example, during molding and roll-forming of the foam. In general, a clip may experience temperatures as low, or lower than −40 F and as high as 180 F, or higher.
It should be noted also, that the process of inserting clips into a foam mold cavity, used for example to form seat parts, is typically a manual operation that is time-consuming, labor-intensive and sometimes subject to inaccurate placement. Clips are dispensed from inside loosely packed boxes, and each one must be individually picked, reoriented properly, and inserted into the appropriate location in the mold cavity for subsequent foam application thereover. This process contains inherent inefficiencies that the worker cannot fully overcome. Moreover, loosely packing ganged groups of clips, connected by intermediate connecting segments further complicates handling. It has been found that a loosely packed supply of ganged clips generally assumes a “bird's nest” entanglement that is extremely difficult to unravel. This problem is addressed in the above-incorporated, commonly assigned, U.S. patent application Ser. No. 11/737,362, entitled FESTOONED TRIM CLIP SYSTEM AND METHOD FOR ATTACHING FESTOONED CLIPS TO A SUBSTRATE by providing an effective and novel system and method for joining groups or continuous chains of “festooned” clips together for dispensing to workers and automated devices. This system and method allows the festooned clips to be pulled apart rapidly for insertion into a foam mold cavity.
A significant and increasing concern in the construction and installation of foam-mounted automotive upholstery clips relates to the overall height of the clip with respect to the foam cushion substrate. Improvements in manufacturing processes and foam formulations have allowed the thickness of the foam layer to be reduced in recent years. Such a reduction saves material, thereby reducing costs and decreasing waste at the end of the seat's product life. Reducing cushion thickness also allows for more accurate conformance of the cushion and overlying upholstery to a complex seat contour (e.g. avoiding an overstuffed and/or billowing appearance for the seat). However, thinner foam layers cause conventional height clips (typically 13 millimeters, or higher, from base to top) may protrude visibly from the foam layer when upholstered, and/or become noticeable as a hard, pointy protuberance to a seated individual—particularly an individual of heightened body weight. This may sometimes be referred to as the “princess-and-the-pea” effect.
Simply reducing the height of an existing clip is not a trivial exercise. The materials, dimensions and geometry employed for the clip may not accommodate a smaller-length leg. That is, the shorter the clip leg, the more force that is required to spread the barbs to receive a listing. The legs must exhibit a reasonable pull-out force over a wide range of temperatures (as above) to prevent the seat from detaching. Likewise, the legs and barbs must allow the listing to be passed therethrough during the upholstery-attachment process with the application of reasonably low force by a worker or robot—so as to prevent fatigue to the worker and/or damage to the seat and upholstery. Hence, selection of materials, dimensions and relative geometry between clip components is critical and necessitates a novel approach to the lowered-height-clip's design.
Accordingly, it is desirable to provide a lower-profile automotive upholstery clip that exhibits good chemically activated adhesion to foam, resilience and holding strength over a wide range of field operating temperatures, resistance to breakage during installation of listing beads—while requiring relatively low push-in force to be exerted by the worker. This clip design should lend itself to a variety of multi-clip ganging and festooning arrangements (as described below) so as to make dispensing and installation of the clip easier and more cost-effective.